1. Field of the Invention
The present invention relates to a thin film transistor (“TFT”) substrate and manufacturing method thereof, and more particularly, to a TFT substrate having improved display quality and a manufacturing method thereof.
2. Description of the Related Art
Generally, a TFT substrate is used as a substrate for independently driving each pixel in a liquid crystal display (“LCD”), an organic light emitting diode (“OLED”), etc.
The TFT substrate includes gate lines for transferring a gate signal, data lines for transferring a data signal, TFTs connected to the gate and data lines, and pixel electrodes connected to the TFTs. The gate lines and the data lines generally extend perpendicularly to each other, and a pixel is formed between each pair of adjacent gate lines and pair of adjacent data lines.
The TFT substrate further includes several insulating layers for insulating signal wirings and electrodes. In particular, an organic protective layer is used to insulate a data pattern including the source and drain electrodes of a TFT and a data line from a pixel electrode. An inorganic protective layer may be additionally formed between the data pattern and the organic protective layer.
Metal, used to form the data pattern, may have stains if it is directly exposed to chemicals such as an etchant or developer. Moreover, such metal forms a metal oxide layer by reacting easily to deionized (“DI”) water or moisture in the air.
The metal oxide layer weakens adhesion of the organic protective layer to the data pattern, causing the organic protective layer to be unfastened relative to the data pattern. Moreover, the metal oxide layer debases adhesion of a photoresist to the data pattern and thus the data pattern becomes disconnected. Also, the metal oxide layer makes a data line and a source electrode be shorted, giving rise to pixel defects. Furthermore, since it is impossible to form a minute pattern due to the metal oxide layer, it is difficult to achieve system-on-glass (“SOG”).
As described above, in the TFT substrate having a structure where the data pattern is directly exposed to various chemicals or where the data pattern is in direct contact with the organic protective layer, there occurs various stains and defects, and the display quality of a display device using the TFT substrate deteriorates.